20Mbps should be enough for a couple of HD YouTube TV streams plus general network traffic. Almost all of the streaming services offer trial periods which should give you a good idea of service reliability.

If streaming to your house (netflix/hulu amazon video) you should be fine.

Otherwise, if the speed is 20 Mbps in both directions, you should be fine too.If it's less upstream and you use things like tablo tuner or a plex server, remote viewer may need to adjust their bandwidth.